Electric braking means for producing a fast stop in phonograph motors



Dec. 13, 1949 A. L. ANDERSON ELECTRIC BRAKING MEANS FOR PRODUCING A FAST STOP IN PHONOGRAPH MOTORS 3 Sheets-Sheet 1 Filed April 2, 1945 MN *Q Nu UD Od INVENTOR firihur'L 8077667 62 fln/czei-s 077/ Dec. 13, 1949 ANDE RSQN 2,491,243

ELECTRIC BRAKING MEANS FOR PRODUCING A FAST STOP IN PHONOGRAPH MOTORS Filed April 2, 1945 3 Sheets-Sheet 2- I N VEN TOR. J77-Z72ur Leonarciflndenson JZ ZOW Dec. 13, 1949 A. L. ANDERSON 2,491,243

ELECTRIC BRAKING MEANS FOR PRODUCING A FAST STOP IN PHONOGRAPH MOTORS Filed April 2, 1945 3 Sheets-Sheet 3 AMPLIFIER 6 RE-CTI FIE R I N V EN TOR. rz ur L eon'ar-a? flnczerson Patented Dec. 13, 1949 UNITED STATES PATENT 0F FICE' ELECTRIC BRAKING MEANS FUR PRODUC- ING A FAST STOP IN" PHONOGRAPH MOTORS Arthur Leonard Anderson, Newfiaven, Conn assignor to. The. Soundscriber Corporation,, New Haven, Conn., ,a corporation. of Connecticut" Applicationihprili 2, 1945; SerialzNo. .58.6;108:

4'Clain1s.

This invention'relates to sound recording, and moreparticularly to means for applyinga quick.

brakingaction to a phonograph inductionmotorfor the purpose of rapidly stopping the turntable;

and to avoid Wasting.of-i:.:1e transcribers time in. listening during the reproduction of the. record.

One object of the present invention is to provide a mechanism of the above nature which will avoid the necessity of operating the motor except-during the actual recordingiperiods.

A further object of. this invention is. toprovide an apparatus of'the abovenature employing an alterating current induction motor and having circuits of different natures. wherebyv thefield of. said motor may be suppliedwith direct. current to provide a sudden magnetic brakingactionfor.

stopping the turntableof a. dictating machine.

A further object is to. provide an apparatusv of the above nature inv which the. direct currentior producing the. fasttstop of the turntablemotor is,

obtained by the useof a condenser discharge.

A still further object is to provide an 'improved' apparatus of the aboi/e nature. which will ibe-lrelativeiy inexpensive to manufacture, which: will avoid blank.coastingzperiods on the record, which:

will be simple inconstructio'n, compact,,ornamental in appearance, andvery efiicient and. durable in use.

The device as describedin thepresent, application is an improvement overthe'soundrecording: apparatus described in the prior Patent'No." 2,342;.-

563, issuedto Lincoln Thompson on February22,

1944, entitled Control circuit for soundrecording;

apparatus, which was reissued on February 20, 1945, No. He. 22,606;

The present invention is also an improvement. over the apparatus disclosed in an-application:

filed June 19, 1944, by Theodore H. Nakken, Serial; No. 540,929, entitled Rapid start and stop clutchmechanism for phonographs, patented'May 18, 1948, No. 2,4e1,836.

In order to produce a rapid stopping of the record when the dictator isthrough talking -varisous forms of mechanical clutch brake. mechanisms have been employed in thepast, but thesemechanisins were complicated and expensive, and it was difiicult to avoid momentary oscillations in the speed which would distort the reproduction. Moreover, such mechanisms were liable to jerk the recording mechanism and resultin shocks and jars which also would distort the reproduction.

By means of the present invention, the above. and other disadvantages have been avoided by. providing an apparatus which will produce a fast stop of the turntable motor electricallyv by switching direct current into the field of the turntable induction motor during the stopping period-this action producing a rapid magnetic braking efiect without mechanical shocks. The rectifier system of the amplifier is a good source of such direct.

current, and suchuseis. disclosed in the first form of the presentinvention. In this form a high wattage resistor is venmloyed: to :limit the current.

applied to the motor to prevent overloading the.

. rectifier tubes.

In the second form of the invention, the use of. a high. resistor iseliminated by obtaining the directcurrentfroma circuit in series with they output or" the. power tubes-0t the amplifier.

In the third formof the invention, useis made.

of a condenser whichis charged while the motor; is running. andis dischargedinto the motorduringthe; stopping period. This system has the ad-.. vantage. that-the B-supply isnot applied to the. motor during the. standby periods.

Withthese and other objects inview, which will appear as, the, description proceeds, there have in which the D; C. forapplying magnetic, braking, action is supplied to the motor. from the rectified output stage of the amplifier.

Fig. 3 is a. similar diagrammatic view of; the

circuit connections of another modified form of.

apparatusin which the D. C. braking current is obtained by discharging acondenser resistance network through the phonograph motor.

As in the apparatus disclosed in the above-mentioned Reissue Patent No. 22,606, the present invention includes. an. electronic amplifier which may operate on either A. C. or D. C. anda disk record turntable driven by a motor which may operate only onA. C.

First-i form Referring now to the drawings. in which like reference characters denote corresponding parts throughout the several views, the numeral It (Fig. 1) indicates a recorder cabinet of'adi'ctating machine of the disk record type such as was disclosed in the Patent No. 2,200,866, issued to Lincoln Thompson May 14, 1940; and'reissued September 22, 1942, No. Re. 22183, entitled Apparatus for recording sound on thin disks.

At the rear of the cabinet it, provision is made. ofia fi-prong plug it which. is adapted to be deta-chably connectedto a corresponding 6-aperture socket l2, connected. by a pair of conductors I3,

14 to a Z-prong plug I5. adaptedto be inserted into anA. C. power line (not shown).

The socket I2. has six apertures, five of which.

3 contain active contacts l6, I1, I 8, I 9, 20, and the sixth of which has no contact. The conductor I3 is joined by a wire 2| to the contact I5, and a wire 22 connects the wire 2| to the contact l8.

The conductor [4 is connected by a wire 23 to the contact H. The contacts I9, 20 are connected together by a wire 24.

Provision is made of an A. C.-D. C. amplifier 25 which is connected to a microphone 26 by a pair of conductors 21, 28.' "The output of the amplifier 25 is led by a pair ofconductor's 28a, 28b, to a pair of wires 29, 30, leading to a recording head 3| having a stylus 32 resting upon a thin disk record 33 mounted upon a flat turn-' table 34.

- The turntable 34 is adapted to be driven by an A; C. motor 35 having a driving shaft 36 and a field coil F as indicated diagrammatically in Fig. 1.

The plug II has six prongs 31, 38, 39, 40, 4|, 42, and it will be seen that current will be supplied from the power line through the contacts |6, H to the prongs 31, 38 which lead through wires 43, 44 to an amplifier switch S1 located on the recorder cabinet It. The prong 42 is electrically inactive, and merely serves as a guide member.

The amplifier switch S1 has a pair of pivoted blades 45, 46 connected to the wires 43, 44, and said blades when in closed position, engage a pair of contacts 41, 48, from which a pair of wires 49, 50 supply current to the rectifier tube T of the A. C.-D. C. amplifier 25. The rectifier tube T has a cathode 59a and a plate 591), the former being connected to a condenser 50c joined by a wire 5001 to the conductor 29. A resistance R (which for simplicity represents the load of the filaments of the other tubes of the amplifier) is connected in shunt with the conductors 49, 50, as shown.

The A. 0. motor field coil F is connected at one end by a conductor to a wire 52 leading to the contact 40 of the 6-prong plug The other end of the field coil F leads through a wire 53 to a pivoted blade 54 of a stop switch S5 having a pair of fixed contacts 55, 5B. When the blade 54 is in its right hand position engaging the contact 56, it will be electrically connected by a conductor 51 to the prong 39 of the fi-prong plug I I.

The contact 4| of the plug H is connected by a conductor 58 to a contact 62 of a motor switch S2, which contact 62 is adapted to be engaged by a pivoted blade 59 mechanically connected with a similar blade 60 joined by a conductor 6| to the wire 30 leading to the recording head 3 I.

The switch S2 also has a fixed contact 53 which is connected by a wire 64 to a conductor 65 leading from the conductor 50 to a single pivoted blade 66 of a switch S3, which blade 56 is adapted to engage selectively with a pair of fixed contacts 61, 68. The contact 61 is connected by a conductor 69 to the blade 59 of the switch S2, while the contact 68 is joined to the wire 5| leading to the field coil F of the motor 35.

Provision is also made of a switch S4 having a single pivoted blade adapted to engage the contacts GI, 12, selectively. The blade 10 is joined by a conductor 10a to the cathode 50a of the rectifier tube T. The contact 12 is joined by a conductor 13 to a high resistance R1 electrically connected to the contact 55 of the switch S5. The resistor R1 is adapted to limit the current through the motor 35 and the rectifier tube T during the braking action.

The contact 1| is joined by a Wire, 14 to a resistor R2, which in turn is connected to the conductor 29 leading to the recording head 3|. The resistor R2 for simplicity is intended to represent the D. C. load of the tubes of the amplifier 25.

' It will thus be seen that the switch S1 controls the flow of current to the A. C.-D. C. amplifier 25, and that the switch S2 controls the current applied to the field F of the A. 0. motor 35.

It will also be seen that when the blade 59 of the switch S2 engages its contact 62, the blade will be out of engagement with its contact 63, and vice versa.

Moreover, the conductors 29, 30 will be connected together by the wires 55 and 54, blade 60, and wire 5| when the motor is shut off so as to short-circuit the output of the A. C.-D. C. amplifier during pauses in the dictation when the motor is not running. The possibility of acoustical iced back between the microphone and the recording head will thereby be prevented in a manner similar to the disclosure in the Patent No. 2,342,503, previously mentioned.

Operation of first form In operation, during dictation, when the turntable 34 is being rotated by the motor 35, current supplied to the rectifier tube T will flow in the following circuit: from supply plug l5 through conductors i4, 23, 44, blade 46 of switch S1, conductors 59, 53d, condenser 50c, cathode 53a, plate 553b, conductors 49, 43, 2|, [3, back to the plug i5.

The motor circuit will be as follows: from the conductor 23 through conductors 44, 59, 65, blade 86 of switch S3, conductor 69, blade 59 of switch S2, conductors 58, 24, 52, 5|, motor field coil F, conductor 53, blade 54 of switch S5, conductors 51, 22, to the conductor 2 l The cathode 500. will be connected through the conductor 13a and the blade 19 of the switch S4 and contact 1| to the high resistor R2.

In the motor stopping position, the B potential supplied by the cathode 59a of the rectifier tube will be applied to the motor field coil F from the cathode 53a through wire 13a to switch blade 10, contact 12, high resistor R1, contact 55, switch blade 54 of switch S5, lead 53, field coil F, lead 5| to contact 38 of switch S3, blade 55, and lead to wire 59.

Direct current from the A. C.D. C. amplifier will thus be applied as a magnetic brake to the field F of the A. C. motor, the resistor R1 serving, as stated above, to limit the D. C. passing through the rectifier tube and prevent overheating of the motor 35 and the recording cabinet It.

It will be understood that the switch blades S2, S3, S4, and S5 may be interlocked by suitable mechanism so that they may be shifted from operating to stopping position and vice verse by a single actuation of a control means for the interlocking mechanism.

Second form In the modified form of the invention shown in Fig. 2, the D. C. used to provide the braking action of the motor 35 is taken from the output stage of the amplifier instead of from the B supply terminals of the rectifier tube of said amplifier as in the first form, shown in Fig. 1.

Power is supplied to the amplifier 25 through a pair of conductors 15, 15, which are connected through the switch S1, conductors 43, 44, plug I, socket |2, wires 2|, 23, and wires l3, [4 to the power plug l5, as clearly shown in Fig. 2.

During the dictation, current is supplied to the motor 35 for rotating the turntable 34 through a circuit similar to that described in the diagram of Fig. l for the first form of the invention.

The motor stopping circuit for the second form, shown in Fig. 2 is also similar to that of 1 the first form except that an additional switch S5 is provided for short-circuiting the recording head 3| when the motor 35 is stopped. The switch So has a blade 99 connected by a conductor I09 to the conductor 05. The blade 99 is adapted to engage an idle contact I! when the motor is operating, and a contact I02 when the motor is stopped. The short circuit is completed through the conductor 30 which is also connected by a conductor I8 to the conductor 65.

This arrangement allows the direct current from the output stage 11 of the amplifier 25fto flow through the field F of the motor 35 when the switches S2, S3, S4, S5, and Se are actuated to produce a fast stopping action upon the motor 35.

The output stage I1 of the amplifier includes a pair of tetrode electron tubes I9, 80, containing cathodes 8|, 82 connected by a conductor--83, and a pair of anodes 84, 85 connected by a conductor 86, a pair of grids 81, 88 connected by a conductor 89, and a pair of grids 90, 9i connected by a conductor 92. The conductor 06 includes a transformer inductance 86a in series therewith, while the conductor 92 includes in series therewith a pair of resistors 93, 94. The conductor 83 is connected to a resistor 95 which in turn is joined by a wire 96 to the blade 10 of the switch S4. Provision is also made of a shunt circuit 91 connected at one end to a junction 91a of the resistors 93, 94 and at the other end to the conductor 96. The shunt circuit 91 also includes a resistor 98 in series therewith.

It will also be understood that the blade 54 of the switch S5, blade 'II) of switch S4, blade 66 of switch S3, and blade 99 of switch S6 may be operated either manually or actuated by means of relays. In the latter case, the relays may be supplied with current from the B-supply of the amplifier 25 and controlled by a switch (not shown) in the microphone 26.

One advantage of the motor-stopping circuit illustrated in Fig. 2 is that the use of the'heavy resistor R1 of the first form shown in Fig. 1 is eliminated. The power consumption will thereby be reduced and the generation of excessive heat in the cabinet avoided.

Third form I In the modified form shown in Fig. 3, D. C. ior

I03, I04, and a resistor I connected therebetween.

The switching from the operating circuit to the stopping circuit will be accomplished in a manner similar to the first two forms of the invention by interlocking control means for actuatin all five of the switches S2, S3, S4, S5, and So simultaneously. During this switching action, the swinging of the blade I0 of switch S4 will cause the condensers I03, I04 (which have previously been charged with D. C. potential from the B- supply of the rectifier tube T of the amplifier) to discharge through the motor 35. The condenser I03 will be rapidly discharged so as to apply a sudden braking action to bring the motor to an initial quick stop. Immediately thereafter,

the condenser I04 will more slowly discharge through the resistor I05 and will provide the remainder of the motor-braking action.

-The condenser-resistor discharge circuit will be so designed as to give the proper discharge period to correlate with the time required for fication several forms in which the invention may be embodied, it is to be understood that these forms are shown for the purpose of illustration only, and that the invention is not to be limited to the specific disclosures, but may be modified and embodied in various other forms without departing from its spirit. In short, the invention includes all the modifications and embodiments coming within scope of the followin claims.

Having thus fully described the invention, what is claimed as new, and for which it is desired to secure Letters Patent, is:

1. In a phonograph recorder, a source of audiofrequency signals, sound record supporting means, an A. C. induction motor for driving said means, an electronic amplifier connected to said source, a recordin head responsive to said amplifier for recording upon said record the amplified sound vibrations received by said source. means to supply A. C. to said motor to drive said record, means for applying the pulsating unidirectional current of the output of said amplifier to the field of said motor for exerting a sudden braking action to rapidly stop said record supporting means and reduce the length of the coasting period, and means to control the amount of the D. C. from said amplifier output supplied to said motor circuit.

2. The invention as defined in claim 1, in which resistance means are employed to control the amount of D. C. from the amplifier supplied to said motor circuit.

3. The invention as defined in claim 1 in which the output stage of said amplifier has a pair oi tetrode electron tubes each containing a cathode, an anode and two grids, and resistance means in said output stage to control the amount of D. C.

"supplied therefrom to said motor circuit. .55

4. The invention as defined in claim 1 in which switch means are provided to simultaneously shut off the supply of A. C. to said motor, supply D; C. to the field of said motor, from the output of }said amplifier and short-circuit the recording head to nullify any howling tendency due to the proximity of said microphone and said recording head.

ARTHUR LEONARD ANDERSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,911,356 Eames May 30, 1933 2,004,893 Hall June 11, 1935 

